Status of SimBlob 2: I have the map working (hexagonal grid, mountains, valleys, water), 2.5d navigation (you move around in 2d and can rotate and zoom, but can't change altitude), and some environmental simulation (springs, water flow, erosion, soil moisture, ground vegetation (grass)). The code is OpenGL+GLUT and should compile for Linux/Mac/Windows, although I've been developing in Linux and haven't tested the other two platforms.